Rolling metal particles to produce compact dense bodies



July 22, 1969 K. CLAUS ETAL ROLLING METAL PARTICLES T0 PRODUCE COMPACT DENSE BODIES Filed April 26, 1967 US. Cl. 29-4205 Claims ABSTRACT OF THE DISCLOSURE A method of rolling aluminum particles into high density shaped pieces which comprises initially rolling such particles to produce a low density strip and at the same time apply a coating of aluminum on to the rolls of a rolling mill and thereafter rolling aluminum particles that have been preheated and applying lubricating and cooling media to the rolls to produce shaped pieces of greater density and strength.

This invention relates broadly to the art of rolling metal particles to produce compact dense bodies, and this application is a continuation-in-part of application Ser. No. 337,672 filed Jan. 14, 1964, and entitled Rolling Fragmentary Aluminium Into Compact Shaped Bodies, now abandoned.

It is known that when rolling aluminum that is compact in sheet form to reduce the thickness there is a risk that in during such rolling, the aluminum stock being rolled may stick to the rolling mill. This tendency to stick or adhere increases with the temperature of the aluminum and also with the amount of roll pressure. For this reason among others, oil or an emulsion of oil and water is supplied, during rolling, to the aluminum stock running between the rolls, or to the rolls themselves, or to both, so that an oil film may be provided to prevent direct contact between the rolls and the aluminum stock in the roll gap.

The same risk of sticking occurs when consolidating by a rolling method, particularly aluminum in the form of granules, shavings or powders, particularly when particulate aluminum is to be formed into solid shaped bodies such as sections, plates or sheets. This is especially true when fragmentary or particulate aluminum is to be con- 3,456,329 Patented July 22, 1969 ice the rolls, that is immaterial. However, when this coherent layer has been formed upon the rolls the subsequent rolling of aluminum particles at high pressure or temperature mediately or shortly after the fragmentary aluminum is rolled at the higher pressure or temperatures. 1

According to the invention it is not sufiicient merely to applythe layer and to roll without oil or oil and water emulsion. Profiles or strips of high density and strength are not then obtained without the stock sticking to the rolls. On the contrary, according to the invention both are necesarythe aforementioned layer upon the rolls, and the application of oil or oil and water emulsion to the layer.

It will be preferable, as is usual in the rolling of co pact aluminum, to employ the oil or the oil and water emulsion at the same time for cooling the rolls.

For the production of the layer, the cold-rolling of aluminum grit has been found to be particularly advantageous. This forms initially a more or less thin layer, which is then subsequently thickened by rolling under increased pressure or at a higher temperature or both.

For the cooling and lubricating under these circumstances it' is advantageous, as in the rolling of compact aluminum, to employ an emulsion of oil in water, preferably an emulsion containing from 2 to 30% of oil. Such an oil mixture can be sprayed onto the layer, or can be applied to the layer in any other suitable manner. In this connection, it is to be noted that the use of an emulsion with too high a proportion of oil diminishes the gripping solidated into a shaped body of a high density and strength in a single pass between rolls since this is possible only by rolling under the relatively high pressures or at rela tively high temperatures or both.

It has now been found that sticking of fragmentary or particulate aluminum to the rolls, for instance, aluminum powder or grit, cannot be prevented when rolling such particles when employing oil or an oil and water emulsion. Surprisingly, however, it has been ascertained that this sticking or adherence can be prevented if a coating of aluminum has been previously applied to the rolls..This coating or layer adhering to the rolls is applied, according to the invention, by rolling aluminum .particles, particularly in the form of small pieces such as powder or grit under a relatively low pressure or at a relatively low temperature or both. When this is done a small quantity of the aluminum adheres to the rolls while a greater quantity forms a shaped piece, sheet or section of comparatively poor quality, that is, it has low density and strength, which shaped piece is subsequently melted down to scrap. If some portion of the powder or grit falls olf power of the coated rolls and often causes the edges of a strip to crack. Too little oil in the emulsion does indeed increase the gripping power, but may lead to overloading the rolling mill and to sticking. The quantitative ratio of oil to water, within the above-mentioned rule, is therefore to be ascertained by testing, according to the circumstances of the individual case.

A modification of the ratio of oil to water may, for instance, be effected by spraying onto the rolls, from a first set of nozzles, such an emulsion as has been found to be suitable for most purposes. From a second set of nozzles there may then be given in addition an emulsion richer in oil, or else the normal emulsion may be diluted by spraying water.

It has been found particularly advantageous not to begin the cooling and lubrication described above immediately before the first rolling of fragmentary aluminum into shaped bodies of high density and strength in one pass, but rather to adopt cooling and lubrication only when the rolls, after the layer is formed, have produced from the fragmentary aluminum, a strip of high density and strength, the length of which corresponds to about three times the periphery of a roll; for if, in the case-of a newly produced layer, immediately upon the first roll ing under high pressure or high temperature, or both, cooling is effected with water, a sticking of the strips may occur. The immediate adoptionof emulsion at the beginning of the rolling may lead to the rolls not gripping to a sufiicient extent.

In a preferred method of carrying out the'invention, the stock, namely granulated aluminum, was heated to temperatures between 400 and 600 C. and rolled in one heat, after the coating layer had previously (been produced by cold-rolling aluminum grit. v

As oil for the production of the oil and water emulsion, a commercially available emulsifiable mineral oil, namely, gasoline 808, was employed. As the lubricating stance may also be used.

As to the analysis and granulation of the granulated aluminum used and of the grit employed, information is given by the appended table. The shavings mentioned in the last column were shavings obtained by milling compact aluminum.

The invention is illustrated by way of example in the accompanying drawings, in which FIGURES 1 and 2 each schematically show one embodiment.

The two rolls represented in FIGURE 1 are driven in the directions indicated by the arrows 1 and 2. The material 3 to be rolled is introduced into the roll gap by one of the known methods. By rolling, a solid shaped body 4, such as a sheet, a plate or a section, is formed. In the direction of the arrows 5 an oil and water emulsion is sprayed on to the rolls, and in the direction of the arrows 6, water exclusively is sprayed on for cooling. Since the cooling is here efiected mainly by water, the quantity of emulsion may be kept considerably less than the quantity of water. The emulsion is as far as possible to be applied to the roll only in a thin layer, in order that no appreciable quantity may enter into the granular material 3 and penetrate between the individual grains, as such layers of emulsion, during the consolidation of the grains into compact bodies, might in some cases occasion cracks, shrinkage cavities or the like.

Example A In carrying out the method illustrated in FIGURE 1, cold aluminum grit of room temperature was initially rolled between rolls 300* mm. in diameter, running at a peripheral speed of meters per minute, to produce a partially consolidated strip (green strip) of small cohesion, 1.5 mm. thick and 5 meters long, corresponding to about 5 revolutions of the rolls.* This treatment produced a coating of aluminum on the rolls. Granules of the grade marked Quality A in the table were then heated to a temperature of 450 C. and rolled, between the rolls thus coated with aluminum, at a rolling speed will be selected in which the proportion of oil is smaller than in the embodiment according to FIGURE 1, for the emulsion must here accomplish at the same time the whole of the cooling, since it is no longer further diluted by, cooling water. Since only small quantities of the lubrieating and cooling medium are to pass into the roll gap, it is particularly desirable, with this arrangement of the nozzles, to provide strippers 8 or squeezing rollers 9, which can be pressed on to the rolls in the direction of the arrows, with an adjustable pressure, and thus keep away from the roll gap at considerable portion of the film of'oil and water emulsion.

Example B In carrying out the invention in accordance with FIG- URE 2, the coating of the rolls with aluminum was effected in the same way as in Example A. Granules of the Quality A were then heated to a temperature of 480 C. and rolled at a speed of meters per minute to produce a strip 4 mm. thick and 120 mm. wide, cooling being effected by spraying an oil and water emulsion containing 2% gasoline 808 in the direction of the arrows 7. The strip had a tensile strength of 9.2 kg. per mm. and an elongation at fracture of 37%.

Example C When employing shavings of the properties indicated in the table, a strip 2.5 mm. thick is obtained. In all other respects this example corresponds to Example B.

The breadth of the gap between the rolls, in practical constructions, is substantially less than that shown in the drawings. With a roll diameter of 300 millimeters, for example, a sheet or plate of a thickness of 6 millimeters can be rolled.

The grit, the granules and the shavings may be stored up in containers at a slightly higher temperature than needed between the rolls and brought to the rolls manually or by conveyor belts.

Analysis, percent:

ides Granulation, percent:

Quality A Granules Quality B Shavings grit grit 11 46 '{8 }Thickness about 0.5-1 mm.

Breadth about 6-8 mm Length about 15-40 mm 22 Bulk density in- Grams/cmfi Percentage of the cast aluminum of 30 meters per minute, to produce a strip 4 mm. thick. During this rolling an emulsion, consisting of gasoline 80S and water in the ratio of 1 to 5, was sprayed toward and on to the coated rolls from nozzles at the rate of 12 cm. per minute for each roll. At the same time, cooling water was sprayed toward and on to the rolls in the direction of the arrows 6 at the rate of 20 liters per minute. This spraying with emulsion and cooling water was, however, not begun until about 2 meters of strip had been produced in the hot-rolling process. The mechanical properties of the strip then produced were: Tensile Strength=9.6 kg. per mm. elongation at fracture=%. These properties correspond to those of conventionally produced material of the same chemical composition.

In a modified method, illustrated in FIGURE 2, oil and water emulsion exclusively is sprayed on from below in the direction of the arrows 7. In this case an emulsion *The pressure between the rolls was 300 kg. for each millimeter of the breadth of the strip.

What is claimed is:

1. A method of rolling fragmentary aluminum into shaped pieces of high density and strength, comprising the steps of coating rolls with a coherent layer of aluminum by rolling fragmentary aluminum into strips of relatively low density and strength under conditions insufiicient to produce a high density strong strip, then, with the rolls so coated, rolling fragmentary aluminum at a suflicient temperature, and applying lubricating and cooling media to the coated rolls to produce said shaped pieces.

2. A method of rolling fragmentary aluminum into shaped pieces of high density and strength as claimed in claim 1, the step of rolling with coated rolls being carried out at a temperature and pressure which is higher than that used to coat said rolls.

3. A method of rolling fragmentary aluminum into shaped pieces of high density and strength, comprising the steps of coating a set of rolls with a layer of aluminum by rolling fragmentary aluminum into strips of relatively low density and strength at a relatively low temperature and a relatively low pressure, then, with the rolls so coated, rolling fragmentary aluminum at a higher pressure, and applying lubricating and cooling media to the coated rolls to produce said shaped pieces.

4. A method of rolling fragmentary aluminum into shaped pieces of high density and strength as claimed in claim 1, the lubricating and cooling being effected by spraying an emulsion of from 2 to 30 percent of oil in water on to the aluminum coating of the rolls.

5. A method of rolling fragmentary aluminum into shaped pieces of high density and strength as claimed in claim 1, the application of lubricating and cooling media to the coated rolls being begun only after the rolling of a shaped piece of high density and strength of a length which corresponds to about three times the periphery of the rolls.

6. A method of rolling fragmentary aluminum into shaped pieces of high density and strength, comprising the steps of coating a set of rolls with a layer of alumi- 2O num by first rolling aluminum grit into strips of relatively low density and strength at a relatively low temperature and a relatively low pressure then, with the rolls so coated, rolling granulated aluminum at a higher pressure and at a temperature of from 400 to 600 C., and then spraying the aluminum coating of the rolls, on the side opposite to the approaching material to be rolled, with a lubricating medium and with cooling Water, such spraying not being begun until after the rolling of a shaped piece of high density and strength of a length corresponding to about three times the periphery of the rolls.

References Cited UNITED STATES PATENTS 2,746,741 5/1956 Naeser 29-4205 2,917,821 12/1959 Fritsch 29-4205 2,922,223 1/ 1960 Boughton 29-4205 3,041,716 7/ 1962 Herenguel 29-4205 3,122,434 2/ 1964 Reed et a1. 29-4205 3,162,708 12/ 1964 Lund et a1 29-420 3,246,982 5/1966 Moritz et al. 75-211 JOHN F. CAMPBELL, Primary Examiner P. M. COHEN, Assistant Examiner US. Cl. X.R. 29-527; 75-211 

